Field of the Disclosure
The present disclosure generally relates to controlling lost circulation in a wellbore during drilling with a drilling fluid. More specifically, embodiments of the disclosure relate to a lost circulation material (LCM).
Description of the Related Art
Lost circulation is one of the frequent challenges encountered during drilling operations. Lost circulation can be encountered during any stage of operations and occurs when drilling fluid (which may include drilling mud) pumped into a well returns partially or does not return to the surface. While some fluid loss is expected, excessive fluid loss is not desirable from a safety, economical, or environmental point of view. Lost circulation is associated with problems with well control, borehole instability, pipe sticking, unsuccessful production tests, poor hydrocarbon production after well completion, and formation damage due to plugging of pores and pore throats by mud particles. In extreme cases, lost circulation problems may force abandonment of a well.
Lost circulation can occur in various formations, such as naturally fractured formations, cavernous formations, and high permeable formations. Lost circulation may also occur due to induced fractures in weak formations. Lost circulation due to induced fractures may occur when the mud weight needed for well control and to maintain wellbore stability exceeds the fracture gradient of the formations. Depleted reservoir formations that have a low fracture gradient may be susceptible to induced loss circulation. Due to the narrow mud weight window for mud used in such formations, drilling of some depleted zones may be difficult without incurring induced loss circulation because the mud weight used to support the formation can easily exceed the fracture resistance of the formation. Induced loss circulation may also occur due to the inability of the drilling mud to remove low and high gravity solids from wellbore. The accumulation of the solids in the mud may increase the fluid density beyond the upper limit of the mud weight window and create induced fractures in the formation, resulting in loss circulation problems.